I'm just curious as to what vehicles would be a suitable donor for everything that I need to do the swap. Mine is a 75 D100 318 4spd with manual brakes and manual steering. I would like to eventually swap out the manual steering and the 4spd for PS and an automatic, and if everything was interchangeable, I'd even do the manual drum brake to power disc brake swap. For now, I'd like to tackle the PS swap. The pump and brackets, hoses and sector, and even the column (hopefully for an automatic) would all be changed along with the pitman arm, if needed. What vehicles and years are compatible, and am I overlooking anything on the swap? Also, would the frame on the D100 be predrilled for the PS gearbox?

I just did it to my 78 D100. Easy peasy. 72-80 stuff will work. Gear boxes mount the same.

Pretty sure you'll need a 73 to 78 or so donor. 2wd and half or light 3/4 ton . Steering changed around 78 and I'm not sure the newer stuff fits. Engine brackets are common get the whole set though.

Brakes are easier, 73 to 84 for rotors and knuckles, newer has a different bolt pattern but also fits. Iirc, boosters swap 73 to 93

72-93 is the platform. Columns changed in 81. The 72-80 columns are actually made by Saginaw. They also use the same Saginaw 808 box as Chevy.

Dodge redesigned the steering linkage on trucks around 78, individual parts are different, not sure if the whole system can swap.

Tilt columns are Saginaw till 90 or so, straight columns are mopar. 90 to 93 is a very different design.

Boxes are Saginaw but iirc there's spline differences between GM and Dodge. There's hose fitting differences that happened around 80.

Center link and tie rod ends changed in 79. Columns changed in 81. The one in my 87 is different than the ones in my 78,79 and 80. I thought they all were Saginaw but maybe not. Chevy and Dodge used the same box. I've swapped between the two. Same part numbers too. W trucks used a reverse rotation box

72-80 2wd 1/2- 1 ton column will work. 4wd is different

Right, that's why I recommend sticking to a same generation donor.